Abstract

Volume increment and ingrowth are important aspects of stand development and regeneration dynamics for determining the effectiveness of uneven-aged silvicultural systems. The main objectives of this thesis were to establish the influence of standing volume on volume increment after different kinds of harvest regimes, the influence of overstorey density on height growth of advance regeneration, and the influence of bilberry (Vaccinium myrtillus L.) on spruce regeneration in managed uneven-aged Norway spruce (Picea abies(L.) Karst.) forests in boreal Sweden. Model simulations with 5-year growth iterations and three harvest regimes of diameter-limit, single-tree selection, and schematic harvests were used to investigate the influence of standing volume on volume increment. Additionally, field experiments at two sites were used. The influence of overstorey density on height growth was established using one of the sites that measured height increments of seedlings, saplings, and small trees in the plots. A field investigation was carried out to establish the influence of bilberry on spruce saplings, which cut bilberry stems in 1 m² circle plots around treated saplings and their height growth compared to the control saplings with uncut bilberry stems. Volume increment increased with increasing standing volume, culminated, and eventually declined. The highest volume increment was found for diameter-limit harvests followed by single-tree selection and schematic harvests. For harvesting a residual stand to 50 m³ha⁻¹, the schematic harvest showed increment losses equalling 25 years of growth. For the field experiments at both sites, standing volume was correlated significantly positively (p<0.05) with volume increment. The height increments for all spruce advance regeneration were better correlated with canopy openness than with basal area or standing volume. Treated saplings decreased in height increment compared to the control during the first and second year after cutting bilberry.